In recent years, in the field of Graphic Arts, new negative acting silver halide photographic elements for duplicating and contacting processes have been introduced. These elements are designed for exposure to UV light on high powered contact frames which are available for exposing lithographic plates and may be handled in ordinary room light (typically in bright white lighting, in which the term "white light" is defined as the emission of a typical commercially available fluorescent lamp).
It is very desirable to produce silver halide photographic elements for duplicating and contacting processes which may be handled safely in bright white light. The benefits of this include ease of working and inspection of the element during exposure and processing, and generally more pleasant working conditions for the operators.
Negative acting silver halide elements which are intended for exposure to UV emitting lamps (such as metal halide lamps) may be afforded some degree of white light handeability by the use of filter dyes either in the emulsion layer or in a non light-sensitive layer. Typically, the dye will particularly absorb visible light and prevent exposure of the radiation sensitive layer by this light. The filter dye is chosen not to greatly interfere with intentional exposure to UV radiations. Examples of silver halide elements incorporating said filter dyes are disclosed in U.S. Pat. Nos. 4,140,531, 4,232,116 and 4,495,274 and EP Pat. Application No. 146,302 where blue absorbing dyes are used which are bleachable during processing.
Additionally, when contacting scanner positive or negative separations, the main objective of a negative acting silver halide photographic element is to obtain a faithful reproduction of the tonal curve. On the other hand, it is normal practice in the field of Graphic Arts to overexpose the first contact to minimize as much as possible retouching and eliminate dirt, spots and paste-up lines. These two objective, that is tonal reproduction and overexposure, are contradictory, i.e., by increasing exposure beyond the optimum time it is possible to eliminate dirt, etc., but a change of dot sizes and the tonal reproduction curve occurs.
Therefore, there is a need in the duplicating and contacting films in the field of Graphic Arts to provide UV sensitive negative acting silver halide photographic elements which have extended exposure latitude to UV light.
Reissue U.S. Pat. No. 30,303 describes UV absorbing dyes useful as filter dyes in photographic elements. The claims are for molecules of the type ##STR1## wherein n is 1 or 2, when n is 1 R.sub.1 and R.sub.2 are independently chosen to represent hydrogen, an alkyl group of 1 to 10 carbon atoms, or a cyclic alkyl group of 5 to 6 carbon atoms provided that R.sub.1 and R.sub.2 cannot both be hydrogen, or R.sub.1 and R.sub.2 taken together represent the atoms necessary to complete a cyclic amino group, and when n is 2 at least one of R.sub.1 and R.sub.2 is alkylene, and G represents an electron withdrawing group.
They are incorporated in silver halide layer(s) or in an UV filter layer of a photographic element. Alternatively, they can be in the film support of the photographic element. The examples given refer to color negative coatings, though black and white constructions are not excluded. No mention is made of water solubilization or bleachability. Their use is to protect the film of unwanted UV exposure and give a more balanced color rendition.
Similar abilities are described in U.S. Pat. Nos. 4,307,184; 4,576,908 and 4,946,768. The first patent refers to polymeric versions of the above dye class and is fairly far removed from our proposed use. The second patent refers to particular versions of formula above in which R.sub.1 and R.sub.2 are allyl groups. The third patent refers to particular versions of the formula above in which R.sub.1 is a short C.sub.1 -C.sub.3 alkyl chain and R.sub.2 is a long alkyl chain &gt;C.sub.10. Advantages are claimed for improved absorption profiles and reduced speed loss compared to the derivatives claimed in Reissue U.S. Pat. No. 30,303. Again their main application is for UV filter dyes in the color negative constructions. Said dyes are hydrophobic and presumably would not be bleached in processing. In fact they are usually preferred to be nonbleachable and nondiffusing to give UV protection after processing. In U.S. Pat. No. 4,307,183 the supersensitizing combination of a polymeric version of formula above with a methine spectral sensitizer in silver halide constructions is claimed.
Of more relevance is U.S. Pat. No. 4,849,326 where water soluble versions of the above dyes are claimed in direct positive (black and white) silver halide constructions. A general formula of water solubilization is used which makes it novel compared to the class and uses disclosed in Reissue U.S. Pat. No. 30,303. Advantages are claimed for improved white light safety with minimal residual UV stain after processing. Water soluble versions of the above dyes are also described in EP Patent Application No. 411,819 for use as antihalation dyes in backing layers of UV-sensitive negative acting silver halide photographic elements. Advantages are claimed for improved dry etching characteristics. In both such references there are no teachings or suggestions that said dyes could be used to improve UV exposure latitude of a UV-sensitive negative acting silver halide photographic element for contact processes, as desired.